190A5 vs 190A8

[PJ_Godzilla]

  Quote, Baumer: "So in essence your argument is, that a front wheel drive car can turn better than a rear wheel drive car since the thrust is forward of the CG."

  -Everybody in the automotive world knows the handling of front-wheel drive cars is vastly different from rear-wheel drive... Ever saw a rear-wheel drive car make a hairpin turn in a Rally? See what happens next when a front-wheel drive car makes the same turn...
  

bad analogy, folks. The rwd tends to be superior in racing primarily because of weight transfer and friction-circle effects. The former means that, on accel, you will transfer weight rearward, thus enabling the generation of greater frictional, tractive force - itself dependent on the normal force on the tire. The latter is best described by a simple thought experiment - or you can try it in your car: how much turning force can your front tires generate when they're locked in braking or spinning under accel?

[Badboy]

Hi Gaston,

Please take the time to read this carefully...

I'm going to explain what happens when you throttle back and reduce power. Take a look at the diagram below.

There are two curves on this diagram that show where a sustained turn is possible across the entire envelope for full power at 1600HP and for a reduced throttle setting of 1000HP.

Notice that when you reduce power, the curve showing all possible best sustained turns moves lower down the envelope, and you can see that means lower sustained turn rates and larger radii.

Specifically, at 225mph the sustained turn rate drops from about 17.8 dps to 12.8 dps a loss of 5dps.  Also, the turn radius increases from about 1100ft to 1500ft. This shows that reducing throttle has a dramatic adverse impact on an aircraft's sustained turning performance by reducing the turn rate and increasing the radius.

You can see all this by examining this diagram:



Similar diagrams to this have been produced since 1932, and they show exactly the same displacement of the sustained turn curve on WWII aircraft as seen above, indicating significantly reduced sustained turn performance with reduction in throttle. But that is not just applicable to WWII aircraft, reduce the thrust on a Prop or a Jet and the sustained turning ability will suffer accordingly. 

I claim it reduces turn RADIUS greatly. Note Karhila says "I turned equally well, but in a smaller radius".

Take another look at that diagram, you will notice that every point on the 1000HP sustained turn curve has a larger turn radius than the 1600HP curve speed for speed. That means if you are at 200mph at full power you could sustain a turn with a radius under 900ft, with reduced throttle at 1000HP that turn would be wider at about 1150ft. You can see this yourself by looking at the diagram. Less throttle leads to worse turn radius, and worse turn rate, period.

As explained before, the only way the anecdotes make sense, or are at least physically possible, is if you interpret them from the perspective of turning at some G limit, and thus instantaneous turns, not sustained turns. The reason that works can also be seen on the diagram above, and here is an example:

Say a pilot is flying at a self imposed 4G limit, he's on the edge of greying out and is using that as his G meter. He doesn't want to pull any harder because he knows that at 4.5G he loses his vision completely after a few seconds, and that could be disastrous, so he's holding 4G at 305mph. At that moment his turn rate is 16dps and his radius is 1600ft. You can see that if he can hold that 4G and reduce his speed to 212mph he will have a turn rate of 23dps and a radius under 800ft. That means he can improve his turn rate and cut his turn radius in half, and of course it would make sense to reduce throttle to try to get to there as soon as possible! 

That's a dramatic improvement, but it only occurs during instantaneous turning conditions. Once you enter a sustained turn, maximum power is required. Why? Because you would rather be at point A than point B on the diagram. Those two points represent the place in the envelope where the best sustained turn can be achieved at 1000HP and 1600HP and you can see at a glance that full power (point A) gives the highest sustained turn rate possible, and the smallest sustained turn radius.   

The problem with your collective misunderstanding of how this works is that you ignore, in the specific wording of the accounts, all the numerous clues that these downthrottled turns are indeed SUSTAINED...

All of the anecdotes you have posted so far are consistent with the facts outlined above. They were real events described by the people who were there, so they should be interpreted by us in a way that is entirely consistent with the laws of physics. That's why the turns being described could not have been sustained turns, because reducing throttle has an adverse impact on sustained turning. So fortunately, there isn't a collective misunderstanding, and the rest of the world hasn't somehow got it all wrong!

Badboy

[PJ_Godzilla]

   All of this would be common knowledge if all jets had their exhausts exiting in the nose... All jet fighter pilots would be today taught to downthrottle in turning combat occurring BELOW Corner Speed if their jets were all nose-tracted... (And that could possibly drive combat speeds down, despite the instantaneous explosive impact of missiles, at least to some extent...) That they might be taught that their principles of fighting was refined in WWII (or even WWI!) may be nice for morale to give them a sense of connection to a glorious past, but it is completely artificial: Nose traction requires you to THINK about turning combat differently...

 

As HTC said, it would be best if you diagram this out. As is, and being no stranger to the free-body diagram, I will attempt to make sense of what you've written here and before with regard to the thrust issue:

1. it is entirely true that the center of thrust will move SLIGHTLY during turning. See my earlier development of the local blade alpha for the aero effect. If you want to determine the inertial impact of trying to change the direction of the rotating prop, I'd ask you to try to get some data on that prop's rotational inertia - though I doubt it differs significantly from most of the other types.

2. I've also shown ,based on HTC's numbers from the F-dub, that the aero effect of displacing the center of thrust is to create a pitch moment of small scale. As HTC also noted, this moment resists aircraft pitch but in no way counters the aircraft turn, itself driven by the large resultant lift force directed at the center of the turn.

3. Thrust does tend to produce a nose up/down (pitch) moment if the center of thrust is displaced vertically, a nose left/right (yaw) if the center of thrust is displaced laterally - this is true if the a/c is a jet or a prop. Your "nose tractive" argument needs to be diagrammed because I see little here to counter the physical reality that the torque scalar (magnitude) is always force X perpendicular distance of perpendicular force x distance.

As for the rest, I think Badboy's nailed it.

[Wmaker]

P.S. Our outboard 30mm package weighs far too much, and our outboard 20mm package doesn't weigh enough, as compared to the real deal. Current bang-for-buck is the 4x20mm, until that is fixed.

According to the A-8 manual found here: http://www.simcentrum.com/pafiledb.php?action=file&id=51, the weight of the outboard cannon ammo is correct to the pound in Aces High at 322lbs.

The cannon weighs 42kg so the weight of the cannons seems to be correct aswell per your weight figures.

[Krusty]

Well according to a number of other sources including technical orders (cited in previous threads on the matter) that weight is wrong.

[Wmaker]

Well according to a number of other sources including technical orders (cited in previous threads on the matter) that weight is wrong.

Would you post those sources?

[Krusty]

As a matter of fact. No. I will not.

There have been at least a half dozen threads on 190s brought back to life or started new in the past month or two. In fact you don't seem to recall the first few pages of this thread (before it spiraled into Gaston-world) where this was already asked and answered.

[Wmaker]

As a matter of fact. No. I will not.

There have been at least a half dozen threads on 190s brought back to life or started new in the past month or two. In fact you don't seem to recall the first few pages of this thread (before it spiraled into Gaston-world) where this was already asked and answered.

I'm trying to collect as many sources as possible to form a complete picture so it would be possible to find out what causes these weight discrepencies.


This table puts AH's 20mm setup as +67 to +77 pounds over weight compared to AH as Baumer mentioned:


From the manual I mentioned:


The weight of the ammo matches AH. And the cannons weight also seems to match AH.

So that is why I asked for the source. Is it the same as Baumers or a separate one?

EDIT/Actually, according to Baumer's mention of the srouce of the table he posted...his table is from the same basic manual (T.2190 A-8)./EDIT

EDIT/Yeh, both of these tables are found from the same manual./EDIT

[Gaston]

Gaston please learn to use correct terms.

1. the word optimal, simply means best. You are mixing 2 concepts.

2.  You say "optimal turn speed", and ("optimal"  sustained turn rate). They are completely different concepts. The key concept being the word SUSTAINED.

Every one here has given you the definition and why 160 is the best sustained turn rate. and 220 being the best turn rate , the key being able to hold the same speed and alt are the different between the concepts.

So the official terms would be best sustained turn rate. And best turn rate.I.E.  Best turn rate & radius happen at corner speed. Best SUSTAINED turn rate & radius happen close to best climb speeds. Corner speed in AH (limited at 6 g's) happens at 2.44 * Stall speed. Corner speed happens at the sqrt(glimit) * Stall Speed.

now many people will leave out the word "Optimal or best" when speaking of sustained turn rates, it is automatically assume the word best or optimal is applied to the sentence or people would stat it more like what rate of climb or turn can be sustained in at 220 mph. But this is not the same concept of best sustained turn rate. It is the same concept when some one states the max speed of a plane, they are leaving out the part that it will only do this speed at one altitude.

If you were to try SUSTAIN a turn at 220 mph (this means not slowing down and not descending) you turn rate would be at least half of what your SUSTAINED turn rate would be sustained at 160 mph. And this is where you are constantly mixing terms. It is conceivable you could get a better turn rate and radius with reduced throttle at corner speed ( sorry I have not crunched the numbers to find out) but this will be at the expense of loosing altitude more quickly, notice we are not using the word SUSTAINED because this is not a sustained turn, we are loosing alt, and there fore will very quickly have to stop the turn, or hit the ground. Hence why the word SUSTAINED is used.


Now as far as you disk loading, could you please draw a simple sketch of this loading you are referring to? If you would I can fairly quickly do the math for you to show you it's net effect with full power and reduced power.


Gaston , it is obvious to me you are truly interested in these topics. I and a few others here know the physics side of this very well, and contrary to your belief, planes do not fly out side of the realm of physics. (If you do not except this concept of physics are true, your hole riser argument also falls apart, because you are trying to make a physics argument as to why the effect is there) If your "Disk riser concepts" is true, then your sketch would very quickly prove it to be true once we crunch some numbers.

HiTech

   -The distinction between peak sustained and peak unsustained turns is very clear in my mind, and I do mention it always...

   -I did not know that the best sustained turn speed of the Me-109G-6 was accepted as being 160 MPH: The replies I got on Il-2 was that the Me-109G-6 had a peak sustained turn rate speed of around 220 MPH, at full power, while the P-51D was a little higher at around 230 MPH. It is true Finnish testing of a Me-109G-2 "peak" at 220 MPH allowed some speed loss, but then the turn was done with a slight CLIMB, so the methodology is peculiar here...

   In any case I had never heard of a peak sustained turn rate at FULL power being as low as 160 MPH before Karhila said so for reduced power... Also I determined that the 6G "Corner Speed" of many WWII prop fighters to be well above 320-340 MPH... This means to me that any downthrottling below near-full max level speed is not an advantage according to accepted theory...

   Note the Me-109G's pilot manual has the sustained turn rate, at full power and at 400 km/h, as being 13 seconds for 180°, or presumably a 26 seconds for a 360°: Very near the maximum sustained turn of 24 seconds in Russian tests, or 22 seconds for the G-2...

   At 450 km/h, still in the Me-109G-6 pilot manual (a whopping 281 MPH), the sustained turn rate abruptly drops to 14 seconds for 100° of turning, so there is an abrupt sustained turn-rate drop of near-50% at a much higher speed than what you say... (I was told this was due to reduced engine acceleration, but I remain open for other contributing explanations for this abrupt drop: Prop disc load, aerodynamics)

   If the sustained turn rate DOUBLED from 220 MPH to 160 MPH, then 24-26 seconds would be 12-13 seconds at 160 MPH... I have never seen such numbers for sustained turns below 200 MPH, or at ANY speed...

   You say 6G "Corner Speed" is 2.44 time stall, but that would only be about 250 MPH on the P-51D Mustang, and wartime testing clearly has an unsustained turn radius of 450 yds (1350 ft.) at 400 MPH for the p-51D (Spit XIV 625 yds), and the 1989 P-51D tests also clearly states "(6G in test) Corner Speed is VERY close to maximum level speed", implying a rapid loss of speed when turning at this (6G?) "structural" limit" ("structural limit" might here mean something a bit higher, like an 7-8G Corner Speed at 400 MPH, which matches the wartime testing of 450 yds. radius at 400 MPH)

   This means to me the lowest speed to be able to reach 6G unsustained, in a P-51D, is at least around 320-350 MPH, and I don't see how this can be consistent with 250 MPH... The absolute structural max. of 7-8G is probaly around 400-420 MPH, which, with fluttering pushing the micro-second loads past 13 Gs, explains why these aircrafts could only be "broken" in dives, and never in level speed flight...

   Also a 6G "Corner Speed" of 320-350 MPH seems consistent to me with a peak sustained turn rate of around 230 MPH at full power for a P-51D...

   This matches, roughly, the Me-109G-6 pilot's manual 26 seconds of sustained 360°s at 250 MPH at full power... (Though the actual 24 seconds sustained "peak" was tested by the Russians at an unknown speed, maybe a bit lower like 220 MPH)

   I am very surprised you find a sustained turn peak for the Me-109G-6 to be at 160 MPH, AT FULL POWER... My impression is that this is not consistent with the actual location of the 6G "Corner Speed" at 320-350 MPH in some types, and the near-best sustained 26 seconds sustained turn time at 250 MPH in the Me-109G-6 pilot's manuals...

   In fact, my impression is that 160 MPH is such a low speed that the Me-109G-6 CANNOT turn hard enough to maintain such a low speed AT FULL POWER without downthrottling... It would be "pulled" faster to a more "natural" and wider-radiused sustained turn speed of over 210-220 MPH at full power... Top speed at full power is 400 MPH, or 360 MPH at lower alts: Can it really turn hard enough at full power, at a sustained 160 MPH, to lose 200 +MPH of straight speed???

   As far as downthrottling accounts go, the notion that this tactic entails a loss of altitude is contrary to the examples I provided of this occurring in flat turns, or at less than 500 ft... I also pointed out that spiraling down to gain angles on a chaser is not a generally sound and acceptable tactic in WWII, since even out-turning in this case is useless because of the lower resulting position compared to the chaser... This is "giving up the high ground", and not really productive at low speeds where zooming or even raising the nose is not easy or available...

   I will provide later some crude graphics about the disc load effect on wing-loading, since my worded explanations are not so helpful...

   Gaston

   

 

   

[hitech]

Gaston do you wish to learn or just keep spouting a complete mix of numbers? If you learn you may be able to start to see when the numbers you are quoting just are orders of magnitudes  incorrect.

Gaston I have flow real mustangs in dogfights. I have pulled 6 g's in them. It is far far below 300 mph. Now you can take my real world pilot account of ME flying the plane, or you can take my physics analysis. Your choice. But the numbers you are mixing and matching to try draw a conclusion is just not even close to accurate. My RV has a 6 g corner speed of about 140. And a stall speed of 58. I have tested both many many times. Again it is about 2.44 ratio, the simple reason it is 2.44 is because 2.44 = sqrt(6) and that is because lift increases with the square of speed.

So Gaston believe your uneducated conclusions, or learn from many of us here who have both done the real thing, and know how to calculate the math. I would much prefer you start trying to apply what Badboy, I and Godzilla are trying to teach you. Because we really have nothing to prove to as to what plane is better, we really do not care.  We love this stuff, and enjoy teaching others the physics.

HiTech

[Gaston]

  I am perfectly willing to admit that the figures I use are inaccurate, but if you can pull 6 Gs unsustained turns far below 300 MPH in a P-51D, why is it that when test pilots tested the P-51D in 1989, with the SAME 6 G limit, they concluded: "The "Corner Speed" is very close to the maximum level speed"...:

   http://bbs.hitechcreations.com/smf/index.php/topic,261798.0.html

  The definition of "Corner Speed" is the lowest speed at which a chosen G limit can be reached... If 3.2 G sustained turns can be done at 250 MPH, it is very believable that near-6Gs turns can be reached "instantaneously" at the same speed, but that still requires you to explain why they said what they said... Which you haven't done except to say that "very close to the maximum level speed" for Corner Speed was "insane"...

  My guess is that you can get pretty close to 6 instantaneous Gs below 300 MPH, say 5.5 Gs, but either the 1989 test pilots had a more stringent standard for "Corner Speed" (more than just barely reaching the value on a G-meter), or they still detected an improving trend towards 6 Gs past 300 MPH... They never went to the absolute 7-8 Gs in those 1989 tests, so their conclusion could be an extrapolation of what they got at 6 Gs. It is not complicated for you to explain what you think they meant... I haven't seen you address what they said.

  Don't expect me to consider your P-51D accounts more authoritative than theirs... This is from the Association of Professional Test Pilots...

  As for the difference between traction and propulsion in turns, here is a crude graphic that explains why traction could not in any way be assumed to perform the same as propulsion, regardless of prop effects or not...

  http://i275.photobucket.com/albums/jj284/gaston11_2008/english-electric-lightning_31.jpg?

  The big issue is that, when thrust is in the nose, the action of pivoting the nose upward REQUIRES that the entire thrust in that nose to be pulled BACK... There is no way around it... When propulsion is in the tail, pivoting the nose up moves the thrust FORWARD...

   Now, I can already see the amounts of forward or backward movements will be decried as being infinitely small... I will again point to the example of a rope holding a weight of 200 lbs: You lift that weight directly with a force of 100 lbs: There is still 100 lbs of tension in that rope...

   To move the thrust BACK, no matter how infinitesimal the amount, you have to beat the ENTIRE thrust coming from the nose: And that lever to beat the thrust is resting of the pivot point of the action: The lift center of the wing...

   And that puts a depressing force on that center of lift, increasing the real-life wing-loading...

   Gaston

   

 

[hitech]

    My guess is that you can get pretty close to 6 instantaneous Gs below 300 MPH, say 5.5 Gs, but either the 1989 test pilots had a more stringent standard for "Corner Speed" (more than just barely reaching the value on a G-meter), or they still detected an improving trend towards 6 Gs past 300 MPH... They never went to the absolute 7-8 Gs in those 1989 tests, so their conclusion could be an extrapolation of what they got at 6 Gs. It is not complicated for you to explain what you think they meant... I haven't seen you address what they said.

Cut and paste there exact wording. I have not seen the document you are referring to. For all I know, if they just said corner speed they could be referring to structural limit corner speed. It is not a question of taking my word over theirs gaston, but rather that the most likely case is you have made an incorrect conclusion from what they wrote. Either way, post the reference and we will see whats up.

   The big issue is that, when thrust is in the nose, the action of pivoting the nose upward REQUIRES that the entire thrust in that nose to be pulled BACK

There is no pushing or pulling of thrust, the rotation of the aircraft is only rotating the prop. The prop is then exerting thrust in a different direction. The forces resisting the rotation are not thrust unless the thrust line would be tilted up when the plane is level causing a pitching down moment. But this torque would be the same no mater what attitude the aircraft is in, but there is no pushing or pulling of thrust, that really is not a physics concept.

The same applies with the jet, when rotating the aircraft there is not any torque by the thrust if the thrust lies on a radial from the CG.  And if it is not aligned then the torque is the same as you are rotating . Other then slip stream effects of a prop causing effects on the tail and wing. The jet will react 100% identical to the prop as long as both lie on the same line.


HiTech

[PJ_Godzilla]

  As for the difference between traction and propulsion in turns, here is a crude graphic that explains why traction could not in any way be assumed to perform the same as propulsion, regardless of prop effects or not...

  http://i275.photobucket.com/albums/jj284/gaston11_2008/english-electric-lightning_31.jpg?

  The big issue is that, when thrust is in the nose, the action of pivoting the nose upward REQUIRES that the entire thrust in that nose to be pulled BACK... There is no way around it... When propulsion is in the tail, pivoting the nose up moves the thrust FORWARD...
 

Nothing is moving backwards. All you're doing with the pitch rotation is slightly decreasing the forward velocity of the upper part of the prop, thus changing its local alpha and slightly increasing its thrust there. I suppose what you say would be true if the ac were fixed but it's not. Even if it were, so long as the line of thrust is aligned to the pivot point, the resultant pitch moment from the pitch perturbation would still be zero. This changes if you can vector the thrust - and that's why a Harrier, for example, can use VIFF maneuvers to point its nose in some pretty wild ways. That doesn't obtain with the BAC Lightning shown nor with our nose pullers that have a line of thrust that points, or very nearly points, through the CG.

Try this: Torque = R X F, where they're both vectors. Or, think of it as Torque = Force x perpendicular distance or = Perpendicular force x distance to get the scalar magnitude.

[Karnak]

Gaston,

WWII aircraft did not produce enough thrust at full throttle to reach their best turn rate as a sustained turn.  That is why the Bf109's (not sure which version, but even from a D to a K the number won't go up too much) best sustained turn speed is 160mph and the best turn rate is 220mph.  Turning that hard produces too much drag for the Bf109 to reach 220mph.  This is true of all WWII aircraft for whatever their best turn and best sustained turn speeds are.  All decreasing the throttle is going to do is slow the aircraft down and force the pilot to slacken off on his turn in order to dedicate more of the wing's lift to keeping the aircraft at its altitude, thus increasing the radius of the turn as well.

Now, a Bf109 moving at 350mph can increase its turn rate and tighten the turn radius by chopping the throttle and using the E stored in inertia until it drops below 220mph.  Ideally, if you were to do that in combat, you'd probably want to go back to full throttle when slightly above 220mph, depending on timing, and absolutely at 220mph so as to retain as much E as possible for as long as possible in the turn.  You'd still be losing E, but the engine would be putting more E back in at full throttle than at 50% throttle, so the rate of E loss would decrease a bit.

Thrustwise, I seem to recall that Widewing said the F4F-4 produced about 1100lbs of thrust and the Spitfire Mk XIV produced about 1750lbs of thrust.

[hitech]

Thrustwise, I seem to recall that Widewing said the F4F-4 produced about 1100lbs of thrust and the Spitfire Mk XIV produced about 1750lbs of thrust.

Karnak thrust on constant speed props varys linearly with speed in normal speed ranges. I.E. Thrust = HP / Speed. So stating what the thrust of a plane is, dosn't really make since unless you include a speed.

HiTech